Degassing of drilling mud



Aug. 16, 1955 J. E. BLISS ET AL DEGASSING 0F DRILLING MUD Filed Oct. 50, 1951 VACUUM PUMP ' WATER 53 SUPPLY 1 23 w 20 HEATING 22 1 $2 CO|L- I 15 FIG. 3

INVENTORS J.E. BLISS A.J. JOSEPH BYHWJQMq A T TORNEKS United States Patent Oflice Ziflifdflfih Patented Aug. 1d, 1955 DEGASSING or DRILLING MUD Jack E. Bliss and Arthur J. .loseph, Midland, Tex., as-

signors to Phillips Petroleum Company, a corporation of Delaware Application ()ctober 3t), 1951, Serial No. 253,943

2 Claims. (Cl. 183-25) This invention relates to the detection of gas and oil bearing strata intersected by a bore hole during the course of drilling operations.

It is well known practice in oil and gas drilling to inspect and examine the mud fluid returns from a well in order to determine the nature of the strata being traversed by the drill, and also the character of the fluid contents, if any, of such strata. Such procedure is of considerable importance because direct evidence of oil and gas has always been and still is the most dependable criterion of a commercial productive well.

in the drilling of oil and gas wells by the rotary method, it is customary to circulate a mud laden fluid down through the drill pipe and out openings in the bottom thereof. This mud laden fluid exerts cooling and lubricating effects on the drill and also picks up and suspends cuttings formed by the action of said drill. This mud, together with the cuttings suspended therein, is returned to the surface through the annular space between the drill pipe and the wall of the bore hole or casing, if casing has been set. At the surface the stream of mud fluid is passed over a shale shaker in order to separate the coarser cuttings from the drill fluid. The fluid in turn passes into a mud pit from which it is recirculated by pumps back through the drill pipe. in the specification to follow, the term occluded is used to describe the condition of retention of the hydrocarbons in the earth sample whether such formof retention be absorption, adsorption, or merely structural envelopment. In order to make use of the occluded gas as an index of the formations traversed by the drill, it is of course necessary to extract said gas from the drilling mud.

Because it is common practice to maintain the drilling mud at a specific gravity such that the hydrostatic head of drilling fluid at the bottom of the hole is greater than any fluid pressure encountered in the formations traversed during the drilling operations, there is very little, if any, flow of fluid from the formation into the drilling fluid. Therefore, the amounts of gases or other hydrocarbons mixed with the drilling fluid from the formations traversed by the drill are usually small thereby resulting in their detection at the surface being accompanied by many difficulties. Since the volume content of combustible gas in drilling mud ranges from negligible amounts up to only several per cent, considerable difliculty has been experienced in the past in providing apparatus capable of separating the gases picked up by said drilling fluid from said fluid for purposes of analysis.

This invention is concerned primarily with those situations in which the gas content of the mud is too small to be noticeable by visual inspection, although there is nothing in the application of the apparatus herein provided which would prevent its use in upper ranges. For example, the routine testing of mud in high pressure areas can be provided to detect dangerous rises in gas concentration which might, if allowed to go uncontrolled, result in a blow out. It is in the range of lower concentrations, however, that the greatest benefits are derived from the analyzer of the present invention because of the difficulty of obtaining direct evidence of oil and gas by any method except the analysis of drilling mud.

The general analytical procedure followed in the removal of this gas from the drilling mud in accordance with this invention comprises pumping mud from either the discharge or suction lines on the rig through a supply line to the field laboratory, by passing a definite volume of mud into the extraction unit, heating the mud in a closed reservoir to an elevated temperature and pressure, flashing the heated content to a water-cooled evacuated chamber, diluting the extracted gas with hydrocarbon-free air to restore the pressure to atmospheric, forcing the diluted gas mixture out of the extraction apparatus through suitable drying tubes into the analytical apparatus by the use of water, and, finally, measuring the combustible content of the mixture by an electrical method.

It is an object of the present invention to provide improved apparatus for extracting occluded gases from drilling mud and testing said gases for combustible content.

Another object is to provide apparatus for automatically transmitting gaseous vapors from a heating chamber into a receiving chamber responsive to the internal pressure developed in said heating chamber.

Still another object is to provide apparatus for carrying out the above mentioned objects which is simple to construct, reliable in result and which employs a minimum number of simple component parts.

Various other objects, advantages, and features of this invention should become apparent to those skilled in the art from the following detailed description of a preferred embodiment of this invention taken in conjunction with the accompanying drawings in which:

Figure 1 is a schematic representation of hydrocarbon mud analyzing apparatus to which the present invention pertains;

Figure 2 illustrates a suitable pressure responsive switch employed in this invention; and

Figure 3 shows schematically the application of the present invention to the hydrocarbon analyzer.

Referring now to the drawing in detail and to Figure 1 in particular, there is illustrated mud separating and analyzing equipment wherein mud from the discharge pipe on the rig enters the intake of pump 10 through the conduit 11 containing an intake valve 12. The mud is directed from pump 10 through a conduit 13 from which a test sample is obtained by opening valves 14 and 15, and partially closing valve 16, thereby causing a portion of the mud stream in conduit 33 to by-pass through the pressure reservoir 17 until it overflows through conduit 18 to drain 20.

The sample comprising a known volume of mud then is isolated in pressure reservoir 17 by closing all of the valves leading to said reservoir. Following this, reservoir 17 is heated by means of an electrical heating coil 21 which is supplied by a source of heating current 22 applied thereto by the closure of switching means 23. To improve the heating conditions a jacket of thermal insulation 24 is provided surrounding reservoir 17. The pressure within reservoir 17 is registered both upon a gage 25 and pressure responsive electrical switch 26, the latter being described in greater detail in conjunction with Figure 2. Heating current is applied to coil 21 until the pressure within reservoir 17 reaches some predetermined value, preferably between 30 and 55 pounds gage which corresponds to a temperature range of approximately to C. Such a temperature is high enough to be effective in driving off the occluded gases and yet low enough to avoid thermal cracking of any oil which may be present. At this preselected pressure, switch 26, which is adjusted to be responsive to said pressure, serves to open valve 27 by means of control device 28 in outlet conduit 29 so as to connect reservoir 17 with a second chamber 38*, which can be either at approximately atmospheric pressure or less, as may be desired. Pump 337i acting through valve 32, conduit 33, and valve 34: serves to evacuate chamber to the desired degree of vacuum which is read from pressure gage 35 communicating with chamber 36. At the same time valve 27 is opened, switching means 23 in the heating coil circuit simultaneously is opened by control means 36 thereby removing the heating current supplied to reservoir 17. Control means 36 also is regulated by pressure responsive switch 26 as described in greater detail hereinafter.

The rush of steam and mud into evacuated chamber 30 carries a large amount of heat which is dissipated rapidly by water circulating in a copper coil 37 surrounding chamber 3% and soldered thereto to make good thermal contact. Vacuum chamber 3t preferably has a volume several times as large as the heated reservoir 1'7 and should be located above it in order that mud and water can run back after the first rush has subsided and the steam condensed.

It should thus be apparent that the foregoing procedure fulfills the three essential requirements for and thorough extraction of occluded gases from the mud: high temperature, agitation, and vacuum. The next step in the analysis procedure is to raise the pressure within vacuum chamber 3% to atmospheric in order that the gaseous mixture can be transferred. conveniently to the analytical unit. This is accomplished by admitting hydrocarbon free air as may be necessary from cylinder 48 through valves 41 and The admission of said air results in a dilution of the gas sample, but this is not important since the analytical method possesses ample sensitivity to measure the combustible content thereof even after dilution. Since the volume of gas extracted from the mud is negligible as compared to the total volume of vacuum chamber 3%, the dilution factor is essentially constant for all samples.

In order to analyze this gaseous sample the gas-air mixture is forced out from vacuum chamber 39 through drying reagents contained in tube 42, and into the combustion unit 43 of an electrical analyzer. This transfer is accomplished either by admitting water through valve 45 into chamber 30 or by an air pump, not shown. To indicate the water level within chamber 38 as the gas is being forced out therefrom, a glass gage 46 is provided which is connected to said chamber by means of suitable packing glands, not shown. The danger of accidentally overflowing chamber 30 by failure of the operator to turn off the water flow at the proper time is eliminated by means of a float 47 in the top of chamber 3 which closes valve 45 before the water rises high enough to do any damage.

The combustion unit 43 contains two essentially identical platinum filaments in separate closed chambers, one of which is sealed in air at atmospheric pressure while the other can be flushed out and filled with a sample of the gas being tested. The two filaments are heated to incandescence by passing an electric current therethrough, and any differential change in resistances due to the burning of combustible gas on one of said filaments is measured by means of an electrical bridge circuit. Suitable analyzing apparatus of this sort is fully described in U. S. Patent 2,349,250, issued May 23, 1944. After the pressure within reservoir 17 falls to a second predetermined pressure, switch 26 functions through control means 28 to close valve 27.

In addition to the equipment above described, facilities are provided for washing out the mud after analysis and for testing both reservoir 17 and vacuum chamber 30 for leaks which may occur therein. Once the test of a given sample is completed, valve 14 at the bottom of reservoir 17 is opened as is valve 48 connecting chamber 30 with reservoir 17, and the mud and water mixture from both chambers is flushed out by means of air pressure applied through conduit 31 A water jet 59 in reservoir 17 is connected to the main water supply through valve 51 and thereby aids in sweeping out any especially heavy or viscous muds contained within reservoir 17. High pressure air may be admitted through valve 52 for the purpose of testing for leaks. As an emergency measure a receptacle 53 is provided at the top of the pressure reservoir 17 and connecting there with through valve 5-4 so that mud samples may be poured downwardly into reservoir 17 from said receptacle 53 in case the mud pump lit? should fail in operation.

The percentage of the gas occluded Within the mud is calculated in terms of a standardizing gas (either propane or butane) used in calibrating the electrical analyzer unit. The comparison samples are obtained by admitting into tank 57, which previously is evacuated, a measured quantity of gas from container 5%, reduced in pressure at valve 559 to atmospheric, and measured within calibration chamber 69. This hydrocarbon gas in calibration chamber se is swept into the storage tank 57 by air from compressed air source 4d being applied through valves 6i and 59, thereby forming a synthetic combustion gas-air mixture of known proportions within storage tank 57. This synthetic mixture alternately can be analyzed by unit 43 to serve as a comparison standard.

Pressure responsive switch 26 is illustrated in gre detail in Figure 2. The operating parts of switch 2d are contained within a cylindrical casing 67 and include a Bourdon tube 68 fixed at one closed end 69' to the casing wall by means of screws 7G. Tube end 69 communic tes with a stem 72 adapted for connection with piu. sure reservoir 17. The free closed end 73 of tube 63 is provided with a bracket 74 secured thereto for pivotally mounting to one end of a switch actuating link 75. Variances in pressure within tube 68 establish a displace ment of link 75 which in turn actuates suitable mechanical linkage (not shown in detail) to tip the mercury tube switch 80. Switch i thereby assumes a position responsive t0 the pressure being measured by said switch. As illustrated, electrodes 81 contained within mercury switch 83 are submerged within a body of mercury thereby completing the electrical circuit through said switch by means of lead wires 83 and Pressure responsive switch 26 initially is adjusted by the setting of pointers 86 and 87 on calibrated slide $8 through rotatable knobs 90 and 91, respectively, protruding outside casing 67. Pointer 86 is adjusted to the first preselected pressure at which switch 26 opens valve 27, while pointer 87 is set to the second lower preselected pressure at which switch 26 closes valve 27. These pointers in turn bias the mechanical linkage contained within switch as in a manner such that mercury switch 80 is tipped at the two preselected pressures. The details of construction of this pressure actuated switch (which does not form a part of this invention per se) are fully disclosed in U. S. Patent 2,043,441, issued June 9, 1936.

In Figure 3 the operation of control units 28 and 36 in response to pressure actuated switch 26 is shown in detail. After the mud sample has been pumped into reservoir 17, switch is closed manually to connect voltage source 22 with heating coil 21. This completed circuit is formed in part through the armature 101 of relay 102. Armature 101 is maintained at its normally open position by means of a suitable tension spring 103. At this time valve 27 is in a closed position. Valve 27, which is a conventional solenoid operated valve, contains a plunger 105 which rests within valve seat 106 in its normally closed position, said plunger 105 being constrained in this position by means of a compression spring 168. Relay winding lit) and solenoid winding 111 are connected in series arrangement with a source of voltage 112 and mercury switch 80 of pressure actuated switch 26. At the instant the first preselected pressure is reached in reservoir 17 mercury switch 80 is tipped to complete the electrical circuit through windings 110 and 111 and voltage source 112. This in turn serves to close armature 101 of relay 102, thereby breaking the circuit to heating coil 21. At the same time, solenoid switch 28 is operated to open valve 27 so as to pass the heated vapors from reservoir 17 into vacuum chamber 30. Once the pressure within reservoir 17 falls to the second lower preselected value, mercury switch 80 again is tipped to open the electrical circuit through windings 110, 111 and voltage source 112. This in turn removes the electrical current from winding 111 which once again closes valve 27. Heating current through coil 21, however, is not restored due to the action of catch arm 114 mounted on armature 102 which holds armature 101 closed. Relay 102 must be reset manually before a second sample is analyzed.

From the foregoing description it should thus be apparent that there has been provided in accordance with this invention an improved form of mud analyzer which effectively serves to liberate any gases occluded within the mud sample under consideration. In this regard means have been provided to automatically transmit the gases driven off said mud sample under preselected conditions and to pass said gases into an accompanying analysis chamber. While this invention has been described in conjunction with a present preferred embodiment thereof, it should be apparent to those skilled in the art that various modifications can be made Without departing from the scope of this invention. This is particularly true with regard to the electrical connections in Figure 3. in parallel with voltage source 112,, for example, in place of the series connections shown. It is, therefore, our intention not to be limited to the precise embodiment herein described.

Having described our invention, we claim:

1. In drilling fluid analyzing apparatus including a pressure vessel adapted to receive the fluid to be analyzed, a chamber to collect vapor from said pressure vessel, and a conduit connecting said vessel with said chamber; means for transmitting vapor from said vessel to said chamber comprising in combination, a solenoid valve positioned in said conduit, an electrical heating coil disposed in said pressure vessel, a source of current connected to said coil, a first switch to disengage said current source from said heating coil, a relay to open said switch, and means Relay 110 and switch 27 can be connected to actuate said relay including a current source and a pressure responsive switch connected in circuit with the coil of said relay and with the coil of said solenoid valve, said pressure responsive switch remaining open until a first preselected pressure is reached in said vessel and closing when a second lower preselected pressure is reached in said vessel, said first switch including latching means to retain said first switch open after said second lower pressure is reached in said vessel.

2. In drilling fluid analyzing apparatus including a pressure vessel adapted to receive the fluid to be analyzed, a chamber to collect vapor from said pressure vessel, and a conduit connecting said vessel with said chamber; means for transmitting said vapor from said vessel to said chamber comprising, in combination, a normally closed solenoid valve positioned in said conduit, an electrical heating coil disposed in said pressure vessel to heat the fluid to be analyzed, a first source of current, a relay actuated switch which is closed in the absence of current being supplied to the coil of the relay associated therewith, first circuit means to connect said first current source to said heating coil through said relay actuated switch, a pressure responsive expansion tube communicating with the interior of said pressure vessel, a container having a quantity of mercury and a pair of spaced electrodes disposed therein, means connecting said container to said expansion tube so that said container may be tipped when the pressure in said expansion tube exceeds a predetermined value, the tipping of said container resulting in the mercury therein completing electrical contact between said electrodes, a second source of current, second circuit means connecting said second source of current in circuit with the coil of said relay and the solenoid of said solenoid actuated valve, said second circuit means being completed in part by the mercury between said electrodes when said container is tipped, and a latch associated with said relay to retain said relay actuated switch open once said relay is energized.

References Cited in the file of this patent UNITED STATES PATENTS 2,043,441 McCabe June 9, 1936 2,362,805 Doan Nov. 14, 1944 2,515,879 Korn July 18, 1950 

1. IN DRILLING FLUID ANALYZING APPARATUS INCLUDING A PRESSURE VESSEL ADAPTED TO RECEIVE THE FLUID TO BE ANALYZED, A CHAMBER TO COLLECT VAPOR FROM SAID PRESSURE VESSEL, AND A CONDUIT CONNECTING SAID VESSEL WITH SAID CHAMBER; MEANS FOR TRANSMITTING VAPOR FROM SAID VESSEL TO SAID CHAMBER COMPRISING IN COMBINATION, A SOLENOID VALVE POSITIONED IN SAID CONDUIT, AN ELECTRICAL HEATING COIL DISPOSED IN SAID PRESSURE VESSEL, A SOURCE OF CURRENT CONNECTED TO SAID COIL, A FIRST SWITCH TO DISENGAGE SAID CURRENT SOURCE FROM SAID HEATING COIL, A RELAY TO OPEN SAID SWITCH, AND MEANS TO ACTUATE SAID RELAY INCLUDING A CURRENT SOURCE AND A PRESSURE RESPONSIVE SWITCH CONNECTED IN CIRCUIT WITH THE COIL OF SAID RELAY AND WITH THE COIL OF SAID SOLENOID VALVE, SAID PRESSURE RESPONSIVE SWITCH REMAINING OPEN UNTIL A FIRST PRESELECTED PRESSURE IS REACHED IN SAID VESSEL AND CLOSING WHEN A SECOND LOWER PRESELECTED PRESSURE IS REACHED IN SAID VESSEL, SAID FIRST SWITCH INCLUDING LATCHING MEANS TO RETAIN SAID FIRST SWITCH OPEN AFTER SAID SECOND LOWER PRESSURE IS REACHED IN SAID VESSEL. 